The present invention relates to a method and device to non-invasively identify hidden foreign objects in proximity of living tissue and more specifically to a method and device that to detect and identify foreign objects hidden under the clothes of a person by measuring an infrared radiation signal emitted by the human subject and by measuring a change in the radiation signal caused by the presence of the foreign object.
The present invention is in the class of methods for structural analysis of multi-component materials. The particular multi-component structures/materials of interest include the following components: a human body (living tissue), clothes, and a foreign object that is composed one or more materials and may include metal, magnetic materials, conductive materials or dielectric materials. Even when the object is hidden behind clothes, the object is positively identified based on the interaction of optical radiation naturally emitted by the human body in the infrared frequency spectrum with every component of the examined object. In addition, magnetic metal detection and reflected light in the infrared (IR), Ultraviolet (UV) or visible spectrums may be employed to supplement identification based on the IR regime.
A living person emits radiation on a wide band of wavelengths. For example, due to its elevated temperature, a human body emits black body radiation in the infrared spectrum. Also the human body reflects radiation in different wavelengths to different degrees. When a foreign object is in proximity of a person, the object affects the radiation field around the person. By sensing anomalies in the radiation field around a person, the present invention detects the presence of foreign objects in proximity to the person including objects hidden behind clothing. Based on the location (including position, as well as shape and size [geometry] of the object) and based on the frequency dependent signature of the radiation anomaly caused by the object, the present invention identifies the foreign object.
There is currently great interest in technologies to quickly detect and identify foreign objects in and around people in a safe, non-intrusive manner. Some important applications of such technologies are detection of weapons and explosives to prevent terrorist attacks and detection of illegal substances by police or customs agents.
Detectors are used to identify and exclude dangerous objects from high security zones (for example the boarding areas of civilian aircraft). Also customs, and drug enforcement agencies use detectors to identify foreign substances hidden in or around the body of a person. Currently popular detectors are metal detectors and x-ray scanners.
X-ray and microwave (penetrating radar) scanners are capable of giving high-resolution pictures of hidden objects. The pictures can be used to positively identify dangerous objects and benign objects. This allows efficient screening so that threats can be detected quickly and with a high reliability without requiring lengthy examinations. Unfortunately, x-rays and microwave radiation have the drawback that they are active methodologies requiring exposing objects to high-energy beams of x-ray or microwave radiation. These x-ray and microwave beams are dangerous to people and cannot be used for scanning objects on or near living humans.
Metal detectors are safe for use in the vicinity of humans but suffer from two drawbacks. First metal detectors only identify one particular class of dangerous object (those made of metal) but cannot identify other dangerous objects (such as organic explosives, plastic or ceramic weapons, various toxic substances or biological agents). Furthermore, metal detectors are non-specific and cannot differentiate between weapons and benign metal objects of common occurrence (e.g. coins, surgical implants, keys, electronic devices, buttons, zippers) Therefore, where metal detectors are used, a (sometimes lengthy) secondary screening is necessary to preclude non-metallic threats and to determine the nature of detected metal objects. Secondary screening may require intrusive methods such as opening and searching personal baggage, removal of shoes hats or religious apparel and even in some cases strip searches. Such intrusive methods are time consuming, inconvenient, may lead to conflict between security personnel and the public. Reliable routine security systems based on such methodologies are extremely expensive and problem prone.
Currently there is interest in developing scanners to non-intrusively detect a large class of dangerous or illegal substances. One method currently under development detects infrared (IR) radiation naturally emitted by a human body and reveals a hidden object by detecting the disturbance caused by the object in the IR radiation field around a person. Current technologies are based on the integral method of IR-thermal analysis. The integral method consists of the following steps:
1) Measure of the space distribution of the integral heat flow from the object most often from the open surface of the body.
2) Reveal and outline anomalies of the heat flow.
3) Calculate the temperature of the surface sections of the analyzed structure.
A wide class of the thermograph devices and systems (e.g. thermo vision [FLIR], thermal cameras, thermographs, radiometers) use the integral mode of thermograph (IR) analysis to detect and map objects. The aim of this method is the structural analysis of the spatial distribution of the flows (usually from narrow bands of IR radiation within the range of 5 μm-14 μm) from the object and mapping the values of thermodynamic temperature of the structure surface. Under certain conditions, the integral method of IR-thermograph analysis may also be used for detecting the presence of foreign objects (metallic or non-metallic) hidden inside clothes by measuring an anomaly of the heat flow. The use of previous art technology for thermal imaging of heat flows to detect hidden objects has the following technical difficulties and limitations:
1) The integral method doesn't allow classification of the substances of which the foreign object is composed. Thus, with previous art integral methodologies, it is possible to detect the foreign object producing the heat flow anomaly, but it is often impossible to identify the detected object.
2) Previous art integral methodologies (e.g. thermal imaging), detect the integral heat flow and its spatial distribution along the surface of the investigated structure without taking into account the difference between radiant characteristics of structural components. Components having different radiant properties and different temperatures may produce the same values of integral heat flow in the wavelength being measured. Therefore, some foreign objects cannot be detected by previous art integral methodologies. Similarly, a homogeneous surface having surface temperature gradient, can give a signal like that of a foreign object.
3) The wavelength range of IR rays used in previous art integral detectors (from 3-5 μm for thermal cameras or 10-14 μm for FLIRs), are absorbed to a considerable extent by clothes. Therefore, previous art integral mode detectors are not well suited for detecting foreign objects hidden under clothes.
There is thus a widely recognized need for, and it would be highly advantageous to have, a non-intrusive detector that is safe to use in the presence of people and can positively identify a variety of dangerous objects hidden behind clothing and quickly and reliably distinguish dangerous objects and dangerous substances from benign objects.
The present invention solves the above limitations because the present invention detects the presence of anomalies in radiation over a wide frequency band. Thus, even when some radiation bands are blocked by clothing or masked by temperature differentials, the signature of the foreign object on the remaining bands will be detected. Furthermore, the present invention teaches measuring radiation using a differential measure of radiation intensity. A differential measure (for example intensity contrast) quantifies the difference between measured values. An absolute measure (for example heat flow) quantifies measured values directly. The use of a differential measure of radiation intensity (e.g. contrast in radiation intensity) makes the present invention more sensitive to subtle anomalies in radiation than previous art methodologies based on absolute measures of radiation intensity (e.g. thermal imaging using a FLIR or a thermal camera). The advantages of using contrast to detect anomalies in radiation is set forth in A. T. Nesmyanovich, V. N. Ivchenko, G. P. Milinevsky, “Television system for observation of artificial aurora in the conjugate region during ARAKS experiments”, Space Sci. Instrument, vol. 4, 1978, pp 251-252; and in N. D Filipp, V. N. Oraevskii, N. Sh. Blaunshtein, and Yu. Ya. Ruzhin, Evolution of Artificial Plasma Formation in The Earth's Ionosphere, Kishinev: Shtiintsa, 1986, 246 pages, which are incorporated by reference for all purposes as if fully set forth herein. Finally, the present invention combines information from the integral analysis of radiation with spectral analysis and other inputs to positively identify foreign objects.
Thus, the present invention provides reliable way of detecting, revealing the exact location, the size and form, and identifying the substance of a foreign object hidden under clothes on a human body. This then aids security personal guaranteeing security of transport, sensitive structures or individuals. It also aids in industrial or military security, criminal investigations, control of illegal substances, and custom control of import and export.